1. Field of the Invention
This invention relates to prosthetic devices for connecting tissue, more particularly to a biological replacement ligament which reproduces the function of a natural collateral or cruciate ligament.
2. Background Information
Conventionally, damaged anterior cruciate ligaments are replaced with grafts from other patient tissue, such as tendon tissue. However, in certain circumstances, the fixation of the replacement ligament is not adequate, requiring further surgery. Prosthetic devices have been used in place of natural connecting tissue, but these devices also exhibit unsatisfactory fixation. Further, the prosthetic devices do not function as would the natural anterior cruciate ligament.
U.S. Pat. No. 5,147,400 discloses a ligament prosthesis which is intended to approximate the biomechanical characteristics of the natural tissue to be replaced or augmented. U.S. Pat. No. 5,147,400 provides a prothesis having a core composed of a first yarn and a sheath surrounding the core and fabricated by a second yarn. However, when significant tension is applied between the ends of the prothesis, interstitial tearing of yarns may occur, much like tearing of individual fibers of a rope under tension. Further, excessive creep elongation may occur as a result of the extreme forces placed on the ligament. Thus, under extreme stress, the prosthesis may be damaged, and therefore may not exhibit the function of the natural ligament.
As is apparent from the foregoing, state of the art ligament prostheses fail to produce predictable and satisfactory results of reproducing the function of the natural ligament.